Electrical measuring instrument.



No. 627,908. Patented June 27, I899.

N. P. DAVIS- 81; F. CONRAD. Y

ELEC-T'REQAL MEASURING INSTRUMENT. (Application filed; Apn 1, 1899.) (No Model.) 3 Sheets-Sheet I.

H n H I IN VE N T035 iT/OHNE Y.

THE Nonms PETERS co.. mmaumcu wAsHmnYuN. n. c.

No. 627,908. Patented June 27, I899;

H. P. DAVIS '8. F. CONRAD.

ELECTRICAL MEASURING INSTRUMENT.

(Application filed Apr. 1, 1899.) (No Model.) 3 Shaets-Sheet 2.

WITNESSES. /N VE/VTOHS 6% WW m/ 7 W *M W WZ/ I By A;;OHNEY.

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No. 627,908. v Patented June 27, I899.

H. P. DAVIS & F. CONRAD. ELECTRICAL MEASURING msmumgm.

(Application filed Apr. 1, 1899.)

3 SheetsSheet 3.

(No Model.)

lNVENTORS I WITNESSES A TOHNE Y,

UNITED STATES PATENT Fries.

HARRY P. DAVIS, or PrrrsBU e, AND FRANK ooNRAD, or WILKINSBURG,

PENNSYLVANIA, ASSIGNOBS TO THE WESTINGHOUSE ELEorR1c AND MANUFACTURINGCOMPANY, or PENNsYLvANIA.

ELECTRICAL MEASURING INSTRUMENT;

SPECIFICATION forming part of Letters Patent No. 627,908, dated June 27, 1899. Application filed April 1, 1899. $erial No. 711,402. (No model.)

the United States, have invented a new and useful Improvement in Electrical Measuring Instruments, (Case No. 816,) of which the following is a specification.

Our invention relates to direct-current electrical measuring instruments, and particularly to instruments of this general class which are employed for indicating the instantaneous values of current or electromotive r 5 force in any given circuit, as distinguished from instruments which are employed for registering or recording the total amount of current or energy traversing a given circuit during a specific interval of time.

The object of our invention is to provide an instrument which shall be simple andcompact in construction, which shall have a uniform scale, be as nearly as possible dead-beat, and the moving parts of which shall be light 2 5 and free from liability to destruction or disarrangement. Y

In the accompanying drawings, Figure 1 is a face view of the instrument, which may be regarded as either a front elevation or a plan 0 view, according to whether the instrument is designed for switchboard use or to be portable, the cover being removed and parts of the frame or casing being broken away. Figs. 2 and 3 are detail views of the principalmovable members of the instrument; Fig. 4 is a sectional viewtaken on line IV IV of Fig. 1,

the indicating-pointer being shown however, in a different position and its controllingsprings being shown in elevation. Fig. 5 is a sectional view on a plane at right angles to that of Fig. 4, the operative portions of the instrument being shown in plan, looking upward, assuming that the device is a switchboard instrument.

Referring now to the details of construction as illustrated in the drawings, the casing l of the instrument may be of any material suitable tothe relations in which the instrument is to be'used and of any convenient or desired shape, the front being provided with a plate of glass or other transparent material 2, which maybe supported in position in any convenient manner and may extend over the Whole or only a portion of the front casing, as may be desired. The field-magnet 3 of the instrument comprises two permanent magnets 3 and 3, which, as shown, are of approximately horseshoe shape; but the shape may obviously be varied from that shown, if desired. Furthermore, it is not essential that the field-magnet be made in two parts. Clamped between one pair of magnet-arms, which are of the same polarity, is the base portion of a polar extension 4, the projecting portion of which extends toward the arms of the magnet of the opposite polarity through approximately a semicircumference. Olamped betweenthe ends of the other two adjacent arms is the base portion of a similar piece 5, which constitutes a polar projection of similar form and dimensions. The extension 5 is in a plane parallel to that of the extension 4 and is separated thereform by an air-gap 6-. These polar extensions 4 and 5 may be of different length from that shown, depending upon the length of the scale desired for the instrument; but in most cases the dimensions shown will be suitable for practical purposes.

The scale-plate 7 of the instrument is supported by two brackets 8 and 9, fastened by means of screwsor bolts to the respective ends of the field-magnet 3, and clamped between the end of each bracket and the corresponding end of the magnet is one side of a rectangular frame 10, whichsupports the bearing-pins 11 and 12 for the movable member of the instrument.

The movable member of the instrument comprises a spool or shell 13, preferably stamped from sheet aluminium or other light conducting metal, a damper-plate 13% and two arms 14 and 15, preferably of the same material, either formed integral with the shell or riveted thereto. It will be seen that the shell 13 surrounds or is threaded upon the polar extension 4, and that the damper-plate 13 extends into the air-gap 6 between the polar extensions. Fastened to arm 14 is a pointer 16, the free end of which moves over the scale 7. The free end of arm 14 is bent into the form of a hook 14:,in which is clamped the insulated outer end of a spiral spring 17, the inner end of this spring being fastened to a collet 18, rigidly mounted on the bearingpin 11. This arm 1% is also provided with a steel point 19, which has its bearing in a jewel set in the end of the pin 11. The arm 15 is bent so as to form two right angles and provide'a support in its free end for a steel point 20, which has its bearing in a jewel set in the end of bearing-pin 12. Riveted to this arm 15 is a supplemental arm 21, the end of which is bent to form a book 21, the insulated outer end of asecond spiral spring 22 being clamped in this hook and the inner end of the spring being fastened to a collet 23, rigidly mounted on bearing-pin 12,

The actuating or measuring coil 24 for the instrument is wound upon the spool or shell 13 and has its respective terminals connected to the outer endsofthespiral springs 17 and 22, The binding-posts 25 and 26 of the instrument for connecting the same to the circuit, the current or electromot-ive force of which is to be measured, are connected by means of wires 27 and 28 to the respective bearing-pins 11 and12by means of suitable binding-posts 29 and 30, a current-adjusting ets 34:, supported by the ends of magnet 3 or other stationary portions of the instrument, and through each of these pairs ofslots extendsa bolt 35 for fastening the shield in position. By loosening these bolts the shield may be adjusted in a plane parallel to those of the polar extensions to any position desired in order to provide the proper condition of magnetic field for the movable member of the instrument. It will be seen that the form andarrangement of the stationary portions of the instrument are such as to economize space and provide a durable as well as convenient arrangement of parts.

By forming the shell or spool 13 of a single sheet of metal and so fastening the damperplate 13 thereto as to make the two substane tially a single element electrically we provide a very desirable damping device, which is effective in operation and at the same time so light andwell balanced that there is a mini mum amount of weight on the bearings, and consequently a minimum degree of frictional resistance to the movement of the operating and indicating mechanism. The shape of the damperfplate ismade such as to substantially balancethe moving parts upon the bearings and such as to give the required damping effect during the entire range of movement of the indicating-pointer.

By attaching the inner ends of the spiral springs 17 and 22 to stationary portions of the instrument substantially all of the weight of the springs is taken off the, moving members of the instrument, and the bearingsare thereby relieved of the friction due to the weight of the springs as ordinarily supported in this class of instruments.

It will be understood that the jewel-bearings might be mounted in the movable member and the cooperating points orpins in the stationary portion of the instrument without in any way departing from the invention. It will also be understood that other modifications may be made in the form or location and arrangement of parts without departing from the spirit and scope of the invention.

We claim as our invention 1. In an electrical measuring instrument,a permanent magnet havingcurved, polar entensions superimposed inparallel planes and; separated by an air-gap, in combination with a combined bobbin-shell and damper-plate, said plate being locatedbetween the polarezttensions and said shell surrounding one of said extensions and provided withan-actnating-coil andan indicatingdevioe.

2. In an electrical measuringinstrument, a permanent magnet constitutingthe field-magnetot; the instrument and provided with a pair of superimposed polar extensions separated by an air-gap,in combination with a combined metal shell and damper-plate, said shell surrounding one of said polar extensions andsaid plate locatedand moving in said airap-V In an e ec i al me s r ng nstrumen a permanent magnet havinga pair of. superiinposed, oppositely-projecting polar extensions separated by an air-gap,in combination with a shell or spool provided with a coil forcarrying the current to be measured-and threaded p e f the polar xte ion a mpe iplate extending from said shell or spoolinto the airgap and means for supportingsaid shell and damper-plate for circumferential movement in accordance with thecurrentor electromotive force traversing said, coil,

4. In an electrical Ineasuringinstrument, a permanent magnet having-superimposed polar extensions separated by an air-gap, illCQlIlr bination with a shell and a damper-plate con: stituting a single conducting-body, said shell beingthreaded upon one of said polar pro? jections and said plate projecting-into said air-gap, a measuring=coil on said Shell, an indicating-pointer and means fQI'l sosupporting said parts that they may move circums ferentially in accordance Withthe current or electromotive force traversing said coil,

5. In an electrical measuring instrument, the combination with apermanent .magnet having polar; extensions, of anactuatingmoil threaded upon one of said extensions and journaled in suitable bearings to circumferentially move thereon, and a spiral spring tending to hold said coil in its initial position, the weight of said spring being supported by a stationary part of the instrument.

6. In an electrical measuring instrument, the combination with the movable member of the indicating mechanism, an actuating-coil and a combined supporting and damping device, of a spiral spring interposed between said device and a stationary part of the instrument, the Weight of said spring being sup- I ported by said stationary part.

7. In an electrical measuring instrument, the combination with a permanent magnet having curved polar extensions separated by an air-gap, of a measuring-coil, a combined supporting and dampingframe threaded upon one of saidextensions and projecting into said air-gap, jewel-bearings for said frame and a spiral spring supported by a stationary portion of the instrument and connecting the same to said supporting and damping frame.

8. In an electrical measuring instrument, the combination with a permanent magnet having superimposed polar extensions separated by an air-gap, of a measuring-coil surrounding one of said extensions, a support for said coil provided with a damper-plate, one

or more spiral springs interposed between 36 said support and a stationary part of the instrument, the weight of said spring or springs being supported by said stationary part, and means for indicating the degree of movement of the coil and its support in opposition to 35 said spring or springs.

9. In an electrical measuring instrument, the combination with a permanent magnet having superimposed polar extensions separated by an air-gap, of a measuring-coil sur- 4o rounding one of said extensions and sup ported in jewel-bearings, and one or more spiral springs supported by the instrumentframe and connected at one end to said coil.

In testimony whereof We have hereunto 45 subscribed our names this 30th day of March,

HARRY P; DAVIS. FRANK CONRAD. Witnesses:

WESLEY G. CARR, H. O. TENER. 

